1)Go to the market
2)Open your inventory and click the "house icon"
3)A window will pop up and that will be your SHOP window
4)Write the name of your shop and drag item you want to sell in the blank boxes
5)Once you drag your item in the box, a window will pop up asking you to INPUT your price and the number of pieces you want to be selling(if your selling bunches)
6)After you have arranged the items you want to sell and their corresponding prices, click the 4 character rectangular icon in your SHOP window(paying 1,000 ED) to open up your shop....
Oh yeah October William Event is only 2 weeks only, so perhaps their planning to replace William Space with something after the event >.>